The present invention relates to an indexable cutting insert with a basically triangular shape for the turning of grooves, said insert comprising an upper surface, a lower surface, which is substantially parallel to the upper surface, plus the edge surfaces which connect them. Each cutting corner of the insert is provided with a projection, which carries a cutting edge arranged substantially at right angles to the direction of the groove. The edges of the insert projection, which are connected, to the cutting edge diverge in the direction of the groove so that the projection has a symmetrical shape in relation to the direction of grooving. Each projection is arranged almost entirely outside a triangle which is defined by an imaginary circle which is inscribed round the centre of the insert and which has the outer surfaces of the insert cutting the circle tangentially.
Triangular, indexable inserts for grooving, which are known from prior art, have designs, which require a relatively large amount of cemented carbide. Cemented carbide is expensive and therefore it is economically advantageous if each insert requires as little cemented carbide as possible. The designs of known inserts are such that holders are required with insert seats especially designed for each insert size. Further accessibility with known inserts in confined spaces is very limited.
One object of the present invention is to design an indexable insert so that only a reduced volume of cemented carbide is required for its manufacture.
Another object is to design the geometry of the insert so that they can be formed with a larger volume of insert material under the cutting edge when the tool is to be used for axial grooving. Greater grooving depths thereby become possible.
A further object is to create an insert with three cutting edges, which can be indexed as required.
A further object is to design an insert so that it can satisfactorily manage the first incut during which a long unbroken chip is normally formed.